Rotary pump

ABSTRACT

A rotary pump is provided for supplying pressure fluid to power steering apparatus of a vehicle. The rotary pump is equipped with a control device which comprises the combination of flow control and pressure relief valves for regulating the flow rate and pressure of delivery fluid respectively, the flow control valve including a slidable spool valve which is operably responsive to the pressure differential between the fluid pressure at a venturi throat and the fluid pressure at the downstream of the venturi throat.

mie States @tent nu 3,632,232

[72] Inventors Tamaki Tomita; 3,384,020 5/1968 Searle 417/300 Akira Suzuki, both of Kariya, Japan 2,981,067 4/ 1961 Clark et al. 417/300 [21] Appl. No, 21,828 3,495,539 2/1970 Tomita et al.... 418/248 [22] Filed Mar. 19, 1970 2,748,711 6/1956 Drude 417/300 [45] Patented .19114, 1972 3,099,284 7/1963 Thrap et al. 137/1 17 [73] Assignee Toyoda Koki Kabushiki Kaisha 3,367,354 2/1968 Gallant 417/304 Kann-shi Amm-ken Japan Primary Examiner-William l... Freeh [32] Priority Apr. 1,1969 Atmme Bl M .tz F d & K l

[33] Japan yum, oscovx rie man ap an [54] ROTARY PUMP ABSTRACT: A rotary pump is provided for supplying pressure fluid to power steering apparatus of a vehicle. The rotary pump is equipped with a control device which comprises the combination of flow control and pressure relief valves for regulating the flow rate and pressure of delivery fluid respectively, the flow control valve including a slidable spool valve which is operably responsive to the pressure differential between the fluid pressure at a venturi throat and the fluid pressure at the downstream of the venturi throat.

mamen am 3632232 SHEET l UF 7 mmm SHEET 2 or 7 PATENTE!) Hl 4 W2 V SHEET 3 of 7 PATENTEU ma 4 |912 SHEET S 0F 7 R070@ ROAT/ON NUMBER (mam) VENTURI Tl-IRAT RESERVOIR PO0L VAL VE PUMP PATEmEnJm me 3.632.232

SHEET 7 UF 7 FIG/O no'rAnv PUMP BACKGROUND OF THE INVENTION The invention relates generally to pumps for translating the rotary energy of an engine of a vehicle to the pressure energy of fluid, and more particularly to a rotary pump which is combined with a control device and is suitable for a power steering apparatus of the vehicle.

As is well known, a pump which supplies pressure fluid to power steering apparatus to supplement manual steering torque increases its delivery flow in accordance with the engine speed of rotation as shown by a line a in FIG. 6, since the pump is directly coupled to the engine of a vehicle by usual means.

However, the quantity of the pressure fluid required by the power steering apparatus is very small compared with the total amount of pump delivery flow of the pressure fluid at highspeed ranges of the vehicle and thus excess pressure fluid must be exhausted independently of and without operating the power steering apparatus. There have been provided many devices for maintaining the pump delivery fluid flow constant in accordance with the demands of the power steering apparatus, one of the most sophisticated devices comprising an orifice restrictor in a fluid conduit leading to a delivery port and a slidable spool valve which controls the opening angle of a bypass port from which the excess fluid is exhausted to a reservoir. The spool valve is responsive to the pressure differential between the pressure at upstream andthe pressure at downstream of the orifice restrictor and serves to maintain the pressure differential at constant to thereby obtain substantially constant delivery flow. However, the above-mentioned device has the following drawbacks:

A considerably power loss is unavoidable when the pressure fluid passes through the orifice restrictor; the power consumed in the pump is great, because the maintenance pressure differential between the upstream and the downstream of the orifice restrictor is an essential requirement for controlling the spool valve and thus the pump is required to deliver fluid having higher pressure than that of pressure fluid supplied to the power steering apparatus. Further, a fluctuation in flow rate of delivery fluid due to thermal effect unavoidably occurs notwithstanding this utilization and operation of the spool valve, so that the viscosity of the pressure fluid is changed by and with the temperature change.

SUMMARY OF THE INVENTION It is, therefore, an object of the invention to provide a rotary pump which may reduce the pump drive power by delivering the necessary fluid required independently of the speed of rotation of the pump.

Another object of the invention is to provide a pump cornbined with a control device which is operable to control the flow rate of the delivery fluid by utilizing a venturi effect.

A further object of the invention is to provide a rotary pump which may deliver pressure fluid at substantially constant flow rate by eliminating a fluctuation of the flow rate of the pressure fluid which may be caused by viscosity change of operating fluid due to temperature change.

A still further object of the invention is to provide a rotary pump requiring relatively small spacing therefor.

According to this invention, there is provided a pump having a housing provided with suction zone, a discharge zone and a bypass passage connecting an outlet zone to a reservoir, a rotor rotatably mounted in the housing and a control device, wherein the control device includes a flow control valve comprising a spool valve which is responsive to pressure differential between the fluid pressure at a venturi throat and at the downstream of the venturi throat in a fluid delivery passage to control bypass flow through a bypass passage.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects of the invention, which will become more fully apparent from the following detailed description, may be achieved by the exemplifying apparatus depicted and set forth in the specification in connection with the accompanying drawings, in which:

FIG. l is a longitudinal sectional view of a rotary pump according to the invention taken along the lines l-l in FIG. 2:

FIG. 2 is a sectional view taken along the lines 2-2 in FIG. l;

FIG. 3 is a fractional sectional view taken along the lines 3 3 in FIG. 2;

FIG. 4 is a sectional view of the rotary pump of another ernbodiment according to the invention and corresponds to the sectional view shown in FIG. l;

FIG. 5 is a fractional sectional view taken along the lines 5-5 in FIG. 4;

FIG. 6 is a graph showing the flow characteristic of the pump according to the invention;

FIG. 7 is a hydraulic circuit wherein the rotary pump according to the invention is applied;

FIG. 8 is a sectional view of the rotary pump of another embodiment according to the invention;

FIG. 9 is a sectional View taken along the lines 9 9 in FIG. 8; and

FIG. 10 is a sectional view taken along the lines lll-l0 in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGS 1 and 2, there is provided a cylindrical casing member 12 in a cylindrical bore 11 formed in housing l0. A rotor 13 is mounted for rotation in the casing member 12. A pair of liquid tight discs 14 and l5 engage the opposite ends of the casing member 12 and the rotor 13. The open end of the housing 10 (right end in FIG. 1) is covered by a blocking member 16 urged toward left by a nut 17 which is threadly engaged with the housing 10, whereby discs 14 and 15, casing member 12 and rotor 13 are maintained in their proper positions. A locking member 7l is further threadly engaged with the housing 10 and serves to lock the nut 17 in the housing 10. The housing 10 and the blocking member 16 are provided with coaxial outwardly projected portions 10a and 16a wherein there are provided bearing members 19a and 19 respectively. The bearing member 19 is maintained in its proper position within the projected portion 16a by a snap action ring 16h. A seal member 19b for preventing the leakage of operating fluid is maintained in its proper position within the projected portion 10a by a snap action ring 19C. A drive shaft 18 of the rotor 13, one end of which is coupled to an engine of a vehicle (not shown) by usual means, is supported by the bearing members 19 and 19a. A cam ring 20 of noncircular conformation which constitutes the pump-rotor 13, details of which will later be described, is xed on the drive shaft 18 intennediate the ends thereof.

There is provided a crescent-shaped clearance zone 21a between the inner cylindrical bore 21 of the casing member 12 and the rotor 13. A plurality of axial slots 22 are disposed circumferentially and equidistantly around the inner bore 2l. An abutment 23 is mounted within each of the slots 22 and is urged toward the periphery of the rotor 13 by a compression spring 24 which is interposed between the abutment 23 and the slot 22. By virtue of the slidable engagement of the abutments 23 with the rotor 13 and the sidewalls of the slots 22, the crescent-shaped clearance 21a is separated into a plurality of pump-operating chambers 25. While six such abutments 23 are shown in FIG. 2, it will be appreciated that the number of the abutments are not specifically limited to six in number. A notch 23a is provided on one side of each of the abutments 23, whereby the fluid in pump-operating chambers is led into the rear or outer end of the abutment 23. Especially, as in the case of FIG. 2, the abutments 23 at the right side may be urged by the delivery pressure in the pump-operating chambers toward the periphery of the rotor I3 to achieve a more positive sliding engagement therewith.

On the outer periphery of the cam ring 20 constituting the pump dominant element of rotor 13, there are formed concentric portions Rl and R2 diametrically opposite each other. The first concentric portion R1 is an arc of a circle having the center of the drive shaft 18 as its center with a radius which is almost the same as that of the inner bore 21 of the casing member 12 so as to assure a sliding engagement therewith. The second concentric portion R2 is also an arc of a circle hav ing the same center, but with a radius which is smaller than the inner bore 2l. The two concentric portions aforesaid are connected with opposite smooth surfaces Cl and C2, whereby a crescent-shaped clearance is formed between the rotor 13 and the inner bore 2l as above mentioned. The opposite surfaces C, and C2 will hereinafter be referred to as eccentric portions C l and C2. Connecting points between the concentric portions Rl and R2 and eccentric portions C1, and C2 are varied in smooth conformation to avoid abrupt changes of the curvature. The concentric portions Rl and R2 serve to achieve optimum sealing engagement between the rotor 13 and the abutments 23, since the abutments 23 snugly and smoothly follow the radial changes of the periphery of the rotor 13 whereby the abutments 23 begin their radial displacement after resting on the concentric portions where any radial changes are not present.

A recess 26 connected with a suction channel 27 which is coaxially dropped in the drive shaft 18 is formed on the central portion of the rst eccentric portion C, intermediate the ends of the rotor 13. A recess 28 formed on the second eccentric portion C2 is connected with a delivery channel 29 provided on the outer periphery of the drive shaft 18, the channel 29 being opened to a fluid-collecting groove 30 formed on the sidewall of the housing and the relatively small clearance between the disc and the blocking member 16. Thus, as the discs 14 and 1S are respectively urged toward the opposite ends of the rotor 13 by the pressure of the pressure starting being displaced to the outsides of the discs 14 and 15 from the delivery channel 29, fluid leakage from the pump-operating chambers through between the discs and the opposite ends of the rotor is prevented.

The chambers in suction cycle (shown at the left side in FIG. 2) are separated by the abutment 23, but they are connected with the single suction channel 27 to effect the suction operation of fluid into the pump so that the angular degree of the recess 26 is almost the same as the first eccentric portion C1. 0n the opening edge of the recess 26, there is provided a small convergent groove 3l extending into the concentric portion R1 from the recess 26 in order to avoid abrupt pressure change of fluid within the slot 22 which fluid is about to enter into suction cycle after delivery cycle, the entry of recess 28 is disposed at the point somewhat behind the starting point of the second eccentric portion C2 at the delivery cycle. Moreover, on the edge of the recess 28, there is provided a small convergent groove 32 extending toward the concentric portion R2 from the recess 28. The groove 32 serves to prevent the pulsating change of the delivery fluid pressure by gradually charging the fluid into the operating chamber 25a when the fluid is about to go into delivery cycle.

In the rotary pump according to the invention, the crescentshaped clearance 21a between the rotor 13 and the inner bore 21 of the casing member is substantially divided into a pair of spaces or zones, i.e., an operating space for suction cycle and an operating space for delivery cycle. The operating space for suction cycle corresponding to the first eccentric portion Cl is separated by the abutment 23 into two or three chambers in the preferred embodiment shown in FIG. 2, and the separated chambers are connected with the suction channel 27 by means of the recess 26. The operating space for delivery cycle (right side in FIG. 2) corresponding to the second eccentric portion C2 is connected with the delivery channel 29 by means of the recess 28. When the rotor 13 is rotated in a clockwise direction as shown by an arrow A in FIG. 2, the volume of the operating space for the suction cycle is increased, resulting in the sucking of fluid from the suction channel 27. and the volume of the operating space for delivery cycle is therefore decreased to thereby deliver the fluid into the delivery channel 29.

An outer cover 33 encloses the housing 10 and constitutes a fluid reservoir 34, the opening end of which is sealed by a rubber ring 73 (shown in FIG. l) inserted between said cover 33 and the housing l0 in order to prevent the leakage of fluid therefrom. A removable cap 72 for pouring operating fluid therefrom is provided on the top of the cover 33.

Since the suction channel 27 is disposed coaxially in the drive shaft 18 and the delivery channel 29 is disposed on the outer periphery thereof, the centrifugal force produced by the rotation of the rotor effectuates to increase the mechanical efficiency of the rotary pump so that the centrifugal force function to initiate the suction of the operating fluid from the suction channel 27 to the chambers for the suction cycle is larger than that which tends to prevent the delivery of the operating fluid from the chambers to the delivery channel 29 during the delivery cycle.

The operating fluid is sucked from a suction port 36, opened to the reservoir 34, into the suction channel 27 through an opening 71a provided in the locking member 71 and discharged into the delivery channel 29 and thence, led into a delivery passage 39 in a control device 38 (FIG. 3) through the fluid-collecting groove 30 and a depressed channel 37.

The control device 38 which controls the flow rate and the pressure of the delivery fluid is described referring to FIGS. 1, 2 and 3. A bore 40 is perforated in the housing 10. A connecting member 42 having a delivery port 41 is provided at one end of the bore 40 and a plug member 43 is liquidtight engagement at the other end thereof to cover such bore end. The passage 39 is opened to the bore 40, whereby the pressure fluid delivered into the delivery channel 29 by the pumping action of the rotor 13 is fed into the bore 40. Slidably mounted in the bore 40 is spool valve 44 which is provided with an annular groove on the periphery thereof and a fluid passage 46 connected to said annular groove 80 through a passage 45. The passage 46 is opened to the delivery port 41 through a venturi throat 47 which is reduced in its diameter compared with the surrounding passages to accelerate the pressure fluid passage therethrough. The passages 39, 45 and 46 and venturi throat 47 make up a delivery passage. A small radial aperture 48 is provided at the venturi throat 47 and is further con nected to a small passage 49 in the spool valve which passage 49 is opened to a right chamber or control chamber 44a between the spool valve 44 and the plug 43. There is provided a left pressure chamber 44b between the connecting member 42 and the spool valve 44. In the control chamber 44a, a com pression spring 50 is interposed between the spool valve 44 and the plug member 43 so as to urge the spool valve to the left, i.e., in a direction to close a bypass port 5l. Thus the spool valve 44 is pressed to the left by the force of the spring 50 and the additional fluid pressure fed from the venturi throat 47 through the aperture 48 and the small passage 49 and is pressed to the right by the fluid pressure downstream of the venturi throat 47, whereby the spool valve 47 is displaced by the force di`erential between on the opposite ends of the spool valve. The opening area of the bypass port 51 which is opened to the bore 40 is controlled by the displacement of the spool valve 44. The bypass port 51 which bypasses the excess fluid to the reservoir 34 is led to the periphery of the blocking member 16 through a bypass passage 52 provided in the housing 10 and thence tothe reservoir 34 through the cutaway portion 16C on the rim of the blocking member 16.

Fluid pressure fed to the control chamber 44a from the venturi throat 47 through the aperture 48 and the passage 49 changes in accordance with the speed of the pressure fluid through the venturi throat 47. A drop in pressure at the venturi throat 47 is determined by the fluid speed therethrough, i.e., when the fluid speed therethrough a high, the drop in pressure is large, and when the fluid speed is reduced, the drop in pressure becomes small. This pressure change is fed to the control chamber 44a through the aperture 48 and the passage 49. Thus the spool valve 44 may be responsive to the pressure fluid speed through the venturi throat 47 and effects to maintain the fluid speed constant by controlling the opening degree of the bypass port 5l. Thus the flow rate of the fluid delivered from the delivery port 41 is kept at the value required by a power steering apparatus which is supplied with the delivered fluid to supplement manual steering torque.

However, in the first embodiment, when the rotor is rotated at a fairly high predetermined speed, the quantity of the pressure fluid through the delivery passage is decreased as shown by a line c in FIG. 6. According to experiments performed the predetermined rotation number is more than three to 4,000 r.p.m.

A poppet valve 53 is contained in the housing 10 and urged toward a valve seat 56 in a passage S7 by a compression spring 55 which is interposed between the poppet valve 53 and a plug 54 threadly engaged with the housing 10 as shown in FIG. 5. The poppet valve 53, the spring 55 and the valve seat 56 make up a pilot relief valve of well-known type. The passage 57 is opened to the control chamber 44a to thereby apply the pressure in the control chamber 44a to the poppet valve 53. When the pressure in the chamber 44a becomes higher than the predetermined value determined by the spring S5, the poppet valve 53 is disengaged with the valve seat 56 or moved upwardly against the force of the spring 55, whereby the pressure fluid in the control chamber 44a is vented to the bypass passage 52 through the passage 57 and a hole SS connecting the bypass passage 52 and the pilot relief valve. When the pressure fluid in the chamber 44a is vented to the bypass passage 52, the spool valve 43 is shifted toward right resulting in increase of the bypass fluid flow so that the pressure in the chamber 44a is not compensated by means of the flow resistance of the aperture 48 and the passage 49, while the poppet valve 53 is disengaged with the valve seat 56. Accordingly, the maximum pressure of the delivery fluid does not exceed the predetermined value therefor.

A hydraulic circuit in which the rotary pump according to the invention is applied is schematically shown in FIG. 7.

A second embodiment according to the invention is described referring to FIGS. 4 and 5. The second embodiment is particularly related to a modified venturi tube 147a which is provided outside the spool valve 144. Describing the different portions from the first embodiment, a delivery passage 60 is formed in parallel with bore 140 in the housing 10. The delivery passage 60 and the bore 140 are connected to the depressed channel 37 by a conduit 6l. A spool valve 144 is slidably mounted in the hole 140 and is provided with an annular groove 80 to control the fluid flow exhausted through the bypass port 51 which is connected to a reservoir. Provided in a left chamber or control chamber 1440 is a compression spring 50 which urges the spool valve so as to close the communication between the conduit 61 and the bypass port 51. The delivery passage 60 is connected to a delivery port 141. There is provided a venturi tube 147a having a venturi throat 147 therein at the center of the delivery passage 60. A radial throttle 62 opened to the venturi throat 147 is provided in the venturi tube l47a and is further connected to the control chamber 144a through a passage 63. Thus the fluid pressure at the venturi throat 147 is led to the control chamber through the radial throttle 62 and the passage 63, On the other hand, the fluid pressure at the downstream of the venturi throat 147 is fed to the other chamber at the right end of the spool valve 144 via a passage 64. When the pressure fluid speed at the venturi throat 147 is increased, i.e., the quantity of the pressure fluid through the venturi throat 147 is increased, the pressure drop at the venturi throat 147 becomes larger and then the force differential between the forces imposed on the opposite ends of the spool valve becomes larger to thereby shift the spool valve left to increase the bypass flow through the bypass port 51. When the pressure fluid speed at the venturi throat 147 is decreased, the bypass flow is also decreased. Thus the almost constant flow rate of the delivery fluid through the delivery port 141 is obtained as shown by the line b in FIG. 6. The hydraulic circuit of the modified form which is the same as that of the first embodiment is shown in FIG. 7.

A third embodiment according to the invention which is not provided with the cover 33 surrounding the housing 10 to form the reservoir 34 for operating fluid is described referring to FIGS. 8, 9 and 10. To describe the third embodiment, the same elements and portions described thcretofore are referred to by the same reference numerals as before. A reservoir 234 is provided on the top of a rotary pump of the third embodiment to reduce the spacing occupied by the rotary pump as best shown in FIG. 8. However, the reservoir 234 is shown attached to the housing of the rotary pump and reservoir 234 may be preferably separated from the rotary pump, when a much smaller spacing is required, the spacing for the rotary pump sometimes providing quite an acute problem in a medium or compact car whose engine compartment is in a crowded condition. The housing is separated into two parts, i.e., a front housing 210a and a rear housing 210b which contain a control device 38 therein. A cylindrical casing member 212 is sandwiched between the front 210a and the rear 210b housings which are formed with centering recesses 210C and 210d at opposing ends respectively to thereby accurately locate the casing member 212 with respect to the housings 210a and 210b. The housings and the casing member are tightly connected by a plurality of bolts 204 which are provided through the housing 210a and the casing member 212, and threadly engaged with the rear housing 210b. A drive shaft 218 is rotatably supported by bearing members 219:1 and 219 which are carried by the housings 210a and 2l0b respectively, the drive shaft having the same shape as that of the first embodiment except that a suction channel 27 is further extended left and opened to the periphery thereof to lead the operating fluid leaked through the bearing 219a into the suction channel 27. A ca m ring 20 having the same shape as the first embodiment and constituting a rotor 13 is fixedly mounted on the drive shaft 218 intermediate its ends. A plurality of abutments 23 are received in respective radial slots 22 formed in the inner periphery of the casing member 212 and urged toward the outer periphery of the rotor 13 by means of respective compression springs 24. Disc members 214 and 215 are inserted between the front housing 210a and the casing member 212 and between the casing member 212 and the rear housing 21011, the disc members being liquid tight and engaged with the opposite ends of the ring member 20 and the abutments A fluid-collecting groove 37, to which pressure fluid is discharged from a discharge channel 29 on the periphery of the drive shaft 218, is formed at one end of the rear housing 2ll0b and thence, communicated with the control device 38 through a passage 39 opened to a hole 240. In the rear housing 210b a bore hole 240 is formed, the axis of which bore 240 is arranged in crossing relationship with the axis of the drive shaft 218. The bore 240 is enlarged in its diameter at the center thereof and thence connected to the reservoir 234 through an inlet port 205 and to an inlet chamber 206 around a suction port 36 through a bypass passage S2. A spool valve 244 which serves to control the fluid flow to the inlet chamber 206 through the bypass passage 52 in a manner to maintain the fluid flow through a venturi throat 247 constant is slidably mounted in the bore 240. The spool valve 244 is provided with a radial passage 245 connected with an annular groove and a venturi tube 247 a having the venturi throat 247 therein to lead pressure fluid from the passage 39 to a delivery port 41. The passages 39 and 245 and venturi throat 247 make up a delivery passage. There is provided a small aperture 48 at the venturi throat 247 and a passage 49 to introduce the pressure fluid from the venturi throat 247 to a control chamber 244:1 which is formed between the spool valve 244 and a' plug member 207 screwed to the housing 210b. A compression spring 250 is interposed in the control chamber 244a to urge the spool valve 244 to theright or in a direction to close the communication between the bypass port Sl and the passage 39 as shown in FIG. 9. A pressure relief valve which is the same as that shown in FIG. 3 and heretofore above is connected to the control chamber to maintain the pressure therein at less than a predetermined value. The spool valve 244 in the third embodiment is operable to control the fluid flow exhausted to the inlet chamber 206 through the bypass passage S2 in the same manner as described in the first embodiment so that the regulated flow rate through the venturi throat 247 may be maintained substantially constant and reduced at the predetermined rotation speed of the rotor.

According to the various embodiments of this invention, the flow rate of the delivery fluid from the delivery port is maintained constant even if there is a viscosity fluctuation due to temperature change, which is fairly large in the pump applied to the power steering apparatus, so that the spool valve adapted to control fluid flow through the bypass port is displaced in accordance with the pressure differential between the pressures imposed on the opposite ends of the spool valve, the pressure differential being dependent on the fluid speed at the venturi throat or a drop in pressure at the venturi throat. Moreover, the pump drive power is reduced considerably so that power loss at the venturi throat is smaller than that of the conventional type applied with an orifice restrictor while the pressure differential between the upstream and the downstream of the venturi throat, whereby the pump delivers the pressure fluid having almost the same pressure as that required by the power steering apparatus is not a dominant requirement. Nevertheless, the pressure of delivery fluid from the pump (the pressure at the upstream of the venturi throat) is substantially lowered compared with the conventional type. `Furthermore, the fluid pressure delivered from the delivery port is effectively kept at less than a predetermined value by the pressure relief valve which is adapted to be responsive to the pressure in the control chamber.

Especially, according to the third embodiment, the spacing for the rotary pump, which is quite acute problem in a medium or compact car whose engine compartment is in a crowded condition, is reduced, and particularly when the reservoir 234 is separately provided from the rotary pump, the spacing requirement is further reduced.

While the foregoing description is concerned with the preferred embodiments of the present invention, it will be evident to those skilled in the art that various changes and modifications may be made therein without thereby departing from the basic principle of the invention, and the appended claims are intended to cover all such changes and modifications as fall within the spirit and scope of the invention.

We claim:

l. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising;

a venturi throat provided in the delivery passage connecting said discharge zone to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough;

a bore perforated in said housing and connected to said bypass passage and said discharge zone; and valve means having on the periphery thereof an annular groove to communicate said discharge zone with said bypass passage and slidably mounted in said bore to be resiliently urged in a direction to close the communication therebetween, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.

2. ln a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to Suid suction zone, und u delivery port, the improvement in said control device comprising:

a bore perforated in said housing and connected to said bypass passage and said discharge zone; valve means having on the periphery thereof an annular groove to communicate said discharge zone with said bypass passage and slidably mounted in said bore to be resiliently urged in a direction to close the communication therebetween, and a venturi throat provided in said valve means to connect said discharge zone to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough;

said valve means forming in said bore a control chamber at one end thereof connected to said venturi throat and a pressure chamber connnected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber, provides that pressure fluid passing through said venturi throat is maintained at a regulated flow rate.

3. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge to said suction zone, a delivery port, the improvement in said control device comprising:

a bore perforated in said housing and connected to said bypass passage and to said discharge zone, a valve means slidably mounted in said bore and in said bore forming a pressure chamber at one end thereof and a control chamber at the other end thereof, an annular groove provided on the periphery of said valve means for communicating said discharge zone to said bypass passage,

a resilient means provided in said control chamber for urging said valve means in a direction to close said communi cation between said discharge zone and said bypass passage,

a venturi tube with a venturi throat provided in said valve means and connected with said annular groove at upstream thereof,

said venturi tube being opened toward said pressure chamber at one end of said valve means,

a passage in said valve means for connecting said venturi throat with said control chamber, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure dif ferential between said control chamber and said pressure chamber to provide that pressure fluid passes through said venturi throat and is maintained at a regulated flow rate.

4. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising:

a bore perforated in said housing and connected to said delivery port, said bypass passage and said discharge zone; and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge zone and said bypass passage, said valve means in said bore being formed with a valve passage therein defining a portion of said delivery passage connecting said discharge zone to said delivery port, said valve passage having a venturi throat adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber to provide that pressure fluid passes through said venturi throat and is maintained at a regulated flow rate.

5. A rotary pump combined with a control device comprising a housing, and a suction port, said housing having a bypass passage for leading excess pressure fluid to said suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said ycasing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in said housing and connected to said bypass passage and said discharge channel, and valve means slidably mounted'in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, a discharge passage connecting said discharge channel to a delivery port through said valve means provided with a venturi throat in said valve means which is adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber providing that pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.

6. A rotary pump combined with a control device comprising a housing having a bypass passage for feeding excess pressure fluid to a suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore perforated in said housing and connected to said bypass passage and said discharge channel, valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, and a venturi throat provided in a delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough, said delivery passage being provided exteriorly of said valve means, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber provides that the pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.

7. A rotary pump combined with a control device comprising a front housing, a rear housing, a cylindrical casing member sandwiched between said housings, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to an inlet chamber, a rotor fixed to said drive shaft in said casing member, a delivery port and a delivery passage connecting said discharge channel to said delivery port, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in one of said housings and connected to a bypass passage and said discharge channel, said bypass passage being for bypassing excess fluid from said discharge channel to said inlet chamber, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, said valve means being formed with a ydisplaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber provides that the pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.

8. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising:

a venturi throat provided in the delivery passage connecting said discharge zone to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough; a bore perforated in said housing and connected to said bypass passage and said discharge zone; and

valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge zone and said bypass passage, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.

9. A rotary pump as recited in claim 8, wherein said control device further comprises a pressure relief valve responsive to the pressure in said control chamber to maintain the pressure of the pressure fluid through said venturi throat at less than a predetermined value by venting said control chamber to the reservoir when the pressure in said control chamber rises to the predetermined value.

10. A rotary pump combined with a control device comprising a housing, and a suction port, said housing having a bypass passage for leading excess pressure fluid to said suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in said housing and connected to said bypass passage and said discharge channel, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, a discharge passage connecting said discharge channel to a delivery port through said valve means provided with a venturi throat which is adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.

11. A rotary pump combined with a control device as claimed in claim 10, wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predetermined pressure.

12. A rotary pump combined with a control device comprising a housing having a bypass passage for feeding excess pressure fluid to a suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a

delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore perforated in said housing and connected to said bypass passage and said discharge channel, valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, and a venturi throat provided in a delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough, said delivery passage being provided exteriorly of said valve means, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.

13. A rotary pump combined with a control device as claimed in claim l2 wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predeter mined pressure.

14. A rotary pump combined with a control device comprising a front housing, a rear housing, a cylindrical casing member sandwiched between Said housings, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to an inlet chamber, a rotor fixed to said drive shaft in said casing member, a delivery passage and a delivery port, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a venturi throat provided in said delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of the pressure fluid therethrough, a bore formed in one of said housings and connected to a bypass passage and said discharge channel, said bypass passage being for bypassing excess fluid from said discharge channel to said inlet chamber, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.

15. A rotary pump combined with a control device as claimed in claim 14, wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predetermined pressure. 

1. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising; a venturi throat provided in the delivery passage connecting said discharge zone to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough; a bore perforated in said housing and connected to said bypass passage and said discharge zone; and valve means having on the periphery thereof an annular groove to communicate said discharge zone with said bypass passage and slidably mounted in said bore to be resiliently urged in a direction to close the communication therebetween, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.
 2. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, and a delivery port, the improvement in said control device comprising: a bore perforated in said housing and connected to said bypass passage and said discharge zone; valve means having on the periphery thereof an annular groove to communicate said discharge zone with said bypass passage and slidably mounted in said bore to be resiliently urged in a direction to close the communication therebetween, and a venturi throat provided in said valve means to connect said discharge zone to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough; said valve means forming in said bore a control chamber at one end thereof connected to said venturi throat and a pressure chamber connnected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber, provides that pressure fluid passing through said venturi throat is maintained at a regulated flow rate.
 3. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connectinG said discharge to said suction zone, a delivery port, the improvement in said control device comprising: a bore perforated in said housing and connected to said bypass passage and to said discharge zone, a valve means slidably mounted in said bore and in said bore forming a pressure chamber at one end thereof and a control chamber at the other end thereof, an annular groove provided on the periphery of said valve means for communicating said discharge zone to said bypass passage, a resilient means provided in said control chamber for urging said valve means in a direction to close said communication between said discharge zone and said bypass passage, a venturi tube with a venturi throat provided in said valve means and connected with said annular groove at upstream thereof, said venturi tube being opened toward said pressure chamber at one end of said valve means, a passage in said valve means for connecting said venturi throat with said control chamber, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber to provide that pressure fluid passes through said venturi throat and is maintained at a regulated flow rate.
 4. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising: a bore perforated in said housing and connected to said delivery port, said bypass passage and said discharge zone; and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge zone and said bypass passage, said valve means in said bore being formed with a valve passage therein defining a portion of said delivery passage connecting said discharge zone to said delivery port, said valve passage having a venturi throat adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber to provide that pressure fluid passes through said venturi throat and is maintained at a regulated flow rate.
 5. A rotary pump combined with a control device comprising a housing, and a suction port, said housing having a bypass passage for leading excess pressure fluid to said suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in said housing and connected to said bypass passage and said discharge channel, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, a discharge passage connecting said discharge channel to a delivery port through said valve means provided with a venturi throat in said valve means which is adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber providing that pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.
 6. A rotary pump combined with a control device comprising a housing having a bypass passage for feeding excess pressure fluid to a suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore perforated in said housing and connected to said bypass passage and said discharge channel, valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, and a venturi throat provided in a delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough, said delivery passage being provided exteriorly of said valve means, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber provides that the pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.
 7. A rotary pump combined with a control device comprising a front housing, a rear housing, a cylindrical casing member sandwiched between said housings, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to an inlet chamber, a rotor fixed to said drive shaft in said casing member, a delivery port and a delivery passage connecting said discharge channel to said delivery port, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in one of said housings and connected to a bypass passage and said discharge channel, said bypass passage being for bypassing excess fluid from said discharge channel to said inlet chamber, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, said valve means being formed with a valve passage therein defining a portion of said delivery passage, said valve passage having a venturi throat adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof, whereby said valve means upon being displaced to a position to establish communication in accordance with the pressure differential between said control chamber and said pressure chamber provides that the pressure fluid passing through said venturi throat is maintained at a constant regulated flow rate.
 8. In a rotary pump combined with a control device and having a housing, a suction zone, a discharge zone and a bypass passage operably connecting said discharge zone to said suction zone, a delivery passage and a delivery port, the improvement in said control device comprising: a venturi throat provided in the delivery passage connecting said discharge zone to said delivery porT and adapted to produce a drop in pressure of pressure fluid therethrough; a bore perforated in said housing and connected to said bypass passage and said discharge zone; and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge zone and said bypass passage, said valve means in said bore forming a control chamber at one end thereof connected to said venturi throat and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.
 9. A rotary pump as recited in claim 8, wherein said control device further comprises a pressure relief valve responsive to the pressure in said control chamber to maintain the pressure of the pressure fluid through said venturi throat at less than a predetermined value by venting said control chamber to the reservoir when the pressure in said control chamber rises to the predetermined value.
 10. A rotary pump combined with a control device comprising a housing, and a suction port, said housing having a bypass passage for leading excess pressure fluid to said suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore formed in said housing and connected to said bypass passage and said discharge channel, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, a discharge passage connecting said discharge channel to a delivery port through said valve means provided with a venturi throat which is adapted to produce a drop in pressure of pressure fluid therethrough, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.
 11. A rotary pump combined with a control device as claimed in claim 10, wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predetermined pressure.
 12. A rotary pump combined with a control device comprising a housing having a bypass passage for feeding excess pressure fluid to a suction port, a cylindrical casing member mounted in said housing, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to said suction port, a delivery port, a rotor fixed to said drive shaft in said casing member, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a bore perforated in said housing and connected to said bypass passage and said discharge channel, valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, and a venturi throat provided in a delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of pressure fluid therethrough, said delivery passage being provided exteriorly of said valve means, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber Connected to the downstream of said venturi throat at the other end thereof.
 13. A rotary pump combined with a control device as claimed in claim 12 wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predetermined pressure.
 14. A rotary pump combined with a control device comprising a front housing, a rear housing, a cylindrical casing member sandwiched between said housings, a drive shaft rotatably mounted in said cylindrical casing member and having a discharge channel and a suction channel opened to an inlet chamber, a rotor fixed to said drive shaft in said casing member, a delivery passage and a delivery port, a plurality of abutments received in radial grooves in the inner periphery of said casing member and resiliently pressed against the outer periphery surface of said rotor, and a control device including a venturi throat provided in said delivery passage connecting said discharge channel to said delivery port and adapted to produce a drop in pressure of the pressure fluid therethrough, a bore formed in one of said housings and connected to a bypass passage and said discharge channel, said bypass passage being for bypassing excess fluid from said discharge channel to said inlet chamber, and valve means slidably mounted in said bore and resiliently urged in a direction to close a communication between said discharge channel and said bypass passage, said valve means in said bore forming a control chamber connected to said venturi throat at one end thereof and a pressure chamber connected to the downstream of said venturi throat at the other end thereof.
 15. A rotary pump combined with a control device as claimed in claim 14, wherein said control device further comprises a pressure relief valve responsive to a predetermined pressure in said control chamber for venting the control chamber to said bypass passage, whereby when the control chamber is vented, said valve means is moved in a direction to open said bypass passage more positively for maintaining the pressure in said control chamber at less than the predetermined pressure. 